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Centella asiatica (L.) Urban: A Predominantly Self-pollinated Herbal Perennial plant of Family Apiaceae
Abstract and Figures
Family Apiaceae, also known as Umbelliferae is characterized by its unique inflorescence; the umbel, an aggregation of flowers giving a high visual impact. Because of this impact, umbels are known to attract a variety of insects rendering most of these taxa ‘entomophilous’. Most of the species in the family are thus characterized by large sized umbels aggregating several flowers together. A unique subgroup in this family comprises of taxa with small and in conspicuous umbels not vivid to naked eyes. Centella asiatica Urban, a medicinally important herbal perennial is a part of this assemblage. Contrary to most of the members of family, it bears simple and small umbels comprising of 3-6 flowers only. Events of floral biology depict the species to be weakly protandrous; however a considerable overlap between staminate and pistillate phases ensures autogamy. The species falls under “facultative Xenogamy” catogary with pollen-ovule ratio of 778.5:1. Although small and inconspicuous, the flowers in these umbels are nectariferous and are briskly visited by crawling insects mainly ants of genus Camponotus. Our pollination experiments reveal them to be active pollinators. These aid mainly in geitonogammous pollination, in case autogamy fails due to some reason. The presentation will elaborate on pollination system of this interesting umbellifer.
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... C. asiatica is predominantly self-pollinating in nature, although the possibility of cross-pollination and visits of crawling insects were reported. Based on pollen to ovule ratio, it comes under the category of facultative xenogamy [3]. The plant is economically important due to its pharmacological properties such as anti-inflammatory, antimicrobial, neuroprotective, anticancer, hepatoprotective, cardioprotective, memory-enhancing, wound-healing, immunomodulatory, anti-hyperglycemic and antioxidant activities [4]. ...
... For the conservation and use in breeding a wild species, there must be ample knowledge about their biological and agronomic characteristics. In light of this fact, various research groups have carried out studies on the reproduction [3,17,18], genomic [7], agronomic [19], and plant tissue culture/micropropagation [20] of C. asiatica. Despite these mentioned studies, there is still a knowledge gap regarding the genetic diversity of the species. ...
... This nature of differences is comparable for each locus separately and this disparity between the observed and expected heterozygosity reveals the high possibility of inbreeding. This supports the inference that the occurrence of polyploidy in our study may be due to the genome duplication [39] and it indicates that self-fertilisation is very common (mean F = 0.82) and with only minute levels of outcrossing (mean [t] = 0.11) (Table 1), as supported by a previous study [3]. ...
Background
Around the world, medicinal plants are utilised for various purposes. Centella asiatica is one of the important medicinal plants widely used in many medicinal systems. Nevertheless, analysis of the genetic diversity would pave the way for its most suitable utilisation.Methods and resultsThe present study analyses the genetic diversity and structure of eighty C. asiatica accessions collected from the southern states of India, using ten genomic microsatellite markers. The mean Nei’s gene diversity (0.46) indicates considerable genetic diversity. Analysis of molecular variance (82.48%) exhibited significant genetic variance between samples within the population. The cluster analysis brought out the structure of the analysed populations as three subpopulations based on the genetic differentiation.Conclusions
The study showed significant intra-population variation, predominant inbreeding and population differentiation in C. asiatica. The findings will help better understanding of the genetic structure and gene pool of the plant.
Temporal dioecism is a synchronized flowering sequence with minimal overlap between the pistillate and staminate phases of an individual plant. This strategy allows pollen to be shed before stigmas become receptive, minimizing geitonogamous pollinations and maximizing outcrossing. I studied this condition using Eryngium yuccifolium Michx., a tallgrass prairie perennial species. As a temporaly dioecious species, E. yuccifolium exhibits the following characteristics: 1) an extended pistillate phase, with stigmas becoming receptive only after the anthers have shed pollen and dehisced, 2) synchronized flower heads, 3) numerous flower heads visited by generalist pollinators, and 4) some degree of self-compatibility as indicated by hand pollinations. Finally, results from open and bagged pollinations and high pollen-ovule ratios indicated that the species is xenogamous. This study also found high fruit and seed sets (close to 90%) for E. yuccifolium. However, intense herbivory by the larva of a Gelechiidae moth significantly reduced the reproductive output of the species by destroying 40-60% of flowers and fruits. The results of this study indicate that temporal dioecism can enhance outcrossing and potentially can explain the high fruit and seed set for E. yuccifolium.
Tuberous lomatiums (Lomatium, Umbelliferae) constitute a well-defined infrageneric group that is characterized by adaptation to a short, early spring growing season followed by a long summer drought. All tuberous lomatiums are andromonoecious and all exhibit a pattern of increasing ratios of hermaphroditic to staminate flowers in successively maturing inflorescences. Floral visitation by a variety of Diptera, Hymenoptera, and Coleoptera effects outcrossing and may also mediate geitonogamous selfing. Xenogamy is promoted by protogyny of hermaphroditic flowers, the arrangement of staminate and perfect flowers, and the sequence of floral maturation. Geitonogamy is favored by the morphology of the inflorescences, overlap of the staminate and pistillate stages of different flowers on the same individual, and the behavior of pollinators. Andromonoecy and high pollen production favor both xenogamy and geitonogamy. The floral features of tuberous lomatiums ensure relatively high levels of seed production even though abundance and activity of pollinators may be limited by harsh environmental conditions.
The wild and cultivated forms of Daucus carota L. are andromonoecious and protandrous. The separation of male and female phases is complete at the level of the Mower and the umbel, but the two phases overlap at the level of the full plant, Creating conditions for geitonogamy. At the same time, insect visits between umbels of adjacent plants lead to xenogamy. The extent of overlap between the male and female phases of various umbel orders varies between wild and cultivated carrot. Consequently, there is probably more outbreeding in wild carrot. The chiasma frequency is higher in cultivated carrot. These findings indicate that the meiotic system generates more variability in cultivated carrot whereas the breeding system has the potential to generate greater variability in the wild plant.
The dynamics of nectar production were studied in perfect florets of two varieties (Karzo, Moran) of annual caraway (Carum carvi L., Apiaceae). Florets were protandrous and strongly dichogamous, lasting 7-15 d but producing nectar from the stylopodia for 4-12 d, in an interrupted fashion. Nectar secretion began during a floret's phase of stamen elongation and anther dehiscence. After reabsorption of uncollected nectar, at which point nectary surfaces were completely dry, the two styles elongated and a second bout of secretion commenced during the female phase, up to 5 d later, when a floret became receptive to pollination. During the male and female phases, respectively, 0.392 ± 0.064 μL and 1.083 ± 0.261 μL of nectar of similar solute concentration (844 mg/mL) was produced per ten florets. On a daily basis, florets yielded 1.5-fold more nectar in the female than during the male phase. First-time nectar removal throughout the female phase did not match the sum of nectar quantities from male and female phases combined, suggesting that under natural conditions, any uncollected male-phase nectar, once reabsorbed, is not made available to visitors of the same florets when in the female phase. Nectar-sugar composition differed between bouts of secretion; it was hexose-rich (59.6% fructose, 26.9% glucose, 13.6% sucrose) initially, but hexose-dominant (70.2, 26.8, 3.1) during the female phase. A 5.7-fold difference in mean nectar production per floret occurred among plants.